Lead poisoning is diagnosed using a lead blood test. Children with high risk are tested for lead levels during routine check-ups. Lead levels in the blood are measured in micrograms per deciliter (mcg/dL). A level of 5 mcg/dL indicates unsafe levels in children. Children having high levels around 45 mcg/dL or even higher need immediate treatment. According to the National Institute of Environmental Health Sciences, no amount of lead in the blood is safe. Additional tests include blood tests that look for the amount of iron storing cells in the blood, X-rays and bone marrow biopsy are done.